Such methods and devices are known in various forms, but all without exception involve discontinuous processing. Moreover most appliances of this kind are unsuitable for home use by the end user, primarily because of the large volumes of the storage and cooling vessels required for the cooling and carbonation.
Thus in International patent application WO 94/05407-A1 a device for preparing and dispensing refreshment beverages is proposed in which drinking water is delivered into a vessel flooded with CO.sub.2 in which the water level is detected by sensors and is maintained between a minimum and a maximum value according to the consumption. A circulating pump driven by an electric motor is housed in this intermediate storage vessel and sucks CO.sub.2 gas out of the gas blanket present above the store of water and mixes it into the stored water in the vicinity of the pump. Cooling coils are fixed to the outside of the storage tank and form part of the cooling system and serve to form a jacket of ice inside the storage tank on its side walls, the thickness of which is measured and serves as a control variable for the cooling power. Water carbonated and cooled in the storage tank can be withdrawn therefrom.
Apart from the obviously substantial technical outlay and the volume of the apparatus required, which make this apparatus unsuitable for the end user, especially as a household appliance, the known processor also suffers from considerable disadvantages. These are in particular that at the intended dispensing rate the ice jacket used as the cold capacity accumulator melts, and after it has been used up the dispensing temperature can no longer be maintained at the desired low value, and in addition when the ice jacket is present the beverage dispensing temperature lies uncontrollably at temperatures below 4.degree. C.
Furthermore, from Japanese published patent application JP 53-094 270 a process for carbonation and storage of water is known by which water which has preferably been precooled and brought to a desired pressure level is pretreated with CO.sub.2 and then led into a first pressure vessel flooded with CO.sub.2 and further enriched, and is then collected and stored in a further storage tank, similarly flooded with CO.sub.2. This carbonation plant, too, suffers from the disadvantage of being unsuitable for use as a domestic appliance owing to the large number of its components and their size. Moreover in this case several steps are needed for introducing the gas, namely first during the supply of the liquid, then a post-carbonation in a further step in the first vessel pressurised with CO.sub.2, and finally in the storage tank. The possibility of direct dispensing of the processed water is not available, since the water must first flow through the storage tank.
In DE 30 21 085-A1 a device for impregnation of water with CO.sub.2 is described and illustrated in which the CO.sub.2 and the water are brought together under elevated pressure in a vessel containing a cooling coil, the CO.sub.2 issuing through pores of a porous body and being taken up by the water as it flows in countercurrent.
In this form of a carbonation apparatus the carbonation apparatus concerned is again one which operates with a vessel flooded with CO.sub.2, with the disadvantages explained above. Apart from the fact that such vessels require a large amount of space and are not suitable for end users, particularly households, with this known device, too, it is not possible to change the CO.sub.2 content at short notice owing to the liquid buffer that is required.
On the other hand, while carbonation devices which in respect of their dimensions are suitable as domestic appliances for the end user, so-called lance carbonation devices, are certainly available on the market, these are nevertheless rather inconvenient to use when in particular circumstances drinking water has to be carbonated portionwise which, in order to introduce larger amounts of CO.sub.2, must in addition be separately cooled, since the solubility falls by about 30%, with an increase in temperature of 10.degree. C.